Method of operating internal combustion engines



United States Patent METHOD or OPERATING INTERNAL COMBUSTION ENGINESJesse'B. Patherg, Union, N.'J.,' assign'or to Esso Research -"aridEngineering Company, a corporation of Delaware No Drawing.Applicatin'December 31, 1953 Serial No. 401,692

The present-invention concerns a method of reducing the octane numberrequirement increase that internal combustion engines, andparticularly'automotive engines, experience when they are operated on conventionalgasolines and lubricants. More particularly, it relates to a, method ofpreconditioning automotive enginesby operating them on selected gasolinmand lubricants whereby the engines may thereafter be operated onconventional gasolines and lubricants without incurring undue increasesin their octane number requirements. It especially relates to a methodfor preco'ating the walls of the combustion chambers of an automotiveengine with a material whose presence reduces the amount of carbonaceousdeposits 'that would otherwise beformed thereon by the use ofconventional fuels and lubricants.

The existence of carbonaceous deposits in the combustion chambers ofautomotive engines has been a continuing problem that has confrontedboth the automotive industry and the petroleum'industry. As a result ofextensive research work, it has now been fairly well established thatthe amount and attending harm of these carbonaceous deposits areinfluenced by several factors. First, it has been found that a number ofconstituents contained in conventional gasolines contribute materiallytoward the formation of these deposits. Suchconstituentsin'clude'high'boiling aromatic hydrocarbons, 40 diolefinichydrocarbons, nitrogen compounds, sulfur compounds (especially in leadedfuels), etc.

It has also been established that a number of materials in conventionalautomotive lubricants'are also responsible for the formation of thecarbonaceous deposits. Such materials includethose hydrocarbons thatboil above about 600 F. (at 10 mm.Hg absolute) and that are generallypresent in lubricating oils. They also include bright stock fractions,various conventional, lubricant additives, aromatic-type hydrocarbons,etc.

It has also'been observed that carbonaceous deposits are particularlyapt to develop within the combustion chambers of an automotive enginewhen the engine is operated under mild loading conditions for extendedperiods of time. Conditions such as these occur in the stop-and-go typeof driving that generally prevails in urban districts. High speed orsubstantially full load operation, on the other hand, tends to reducethese carbonaceous deposits.

The carbonaceous deposits that form in the combustion chambersof anautomotive engine have several adverse eflects. They reduce the volumeof each com- 'bustion chamber and thereby increase the compression ratioof the engine. This increase-in compression ratio in turn causes a'proportional increase in the octane number requirement of-the engine.'This increase, however, accounts for'only aboutl'0%20% of the octanenumber requirement increase that can be traced substantially directly tothe presence of'the deposits. The remaining"80%90% of the'octane numberrequirement increase (ORI) appears to result from other factors that areoccasioned by the existence-of the deposits. It is leaded gasoline.

contemplatedfor example that the depositshave' a catalytic effect on thecombustion process that occurs'in each combustion chamber which tends tocause detonation and/or preignition. It is also contemplated that thesedeposits tend to insulate each combustion chamber by decreasing the rateof'heattransfer'through the cylinder walls. This results in heating upthe incoming fuel-andair charge and raises the overall combustiontemperature which in turn makes the engine more prone to knock.

The exact nature or structure of these carbonaceous deposits is stillthe subjectof'much' study and speculation. It has been reasonably wellascertained that the organic portion ofthedeposits generally containscarbon, hydrogen and oxygen in an atomic'ratio of about 5 :5 :2. Thedeposits may 'also contain inorganic constituents as, for example,various lead-compounds when the engine under consideration has'beenoperated on a In theseinstances'the inorganic portion of the'depositsmay comprise up'to about 'to by weight of-the deposits. Even here,however, it is now considered that the presence or existence of'theinorganic deposits may be largely dueto the existence or presence of thecarbonaceous deposits. In other words, the inorganic deposits are heldWithin the combustion chambers by the resin-like structure of thecarbonaceous deposits; and the inorganic deposits can be avoided if thecarbonaceous deposits can first be prevented from forming.

Although the automotive industry and the petroleum industry are aware ofthe existence of the deposits described above, relativelylittle progresshas as yet been made toward a practicaland complete solution to theproblem-of eliminating them. Such a solution isurgent,

since the present alternatives present somewhat of a dilemma. Theautomotive engine'manufactu'rers are reluctant to build engines thathave compression ratios much in excess of 8/1 since'engines of greatercompression ratios than this require very high octane gasolinesafterrelatively short operating periods. Thus, an engine will generallyexperiencean'increaseinits octane requirement (O.R.I.) of 10 to 20octane numbers in 10 to 20,000 miles of its operating life. Thisrequirement increase .presents a very serious problem and, in effect,deprives thegeneral public of theopportunity to take advantage of theincreased operating-economies of high-compression engines.

The petroleum industry on the other hand is faced with the necessity ofproviding extremely high octane fuels (95-100 O.N.) to satisfy enginesof greater than 8/1 compression ratio, unless-a means is found wherebythese engines may operate without knocking on conventional, commercialgradefuels of less than 95 ON. and preferably less than ON. Otherwise,the petroleum refiners will be forced to provide fuels that areextremely expensive and that entail complex refining operations.

Accordingly, it is an object of the present'invention to make availablea means for preconditioning an automotive engine wherebythe engine maybe operated on conventional gasoline-type fuels and lubricants withoutexperiencing an undue increase in its octane number requirement.

It is a particular object of the present invention to provide a gasolinefuel which is to be utilizedin the operation of the engine during itsbreak-in-period and which will thereafter permit satisfactoryperformance of the engine on conventional fuels and lubricants.

These objects may be achieved in accordance with the present inventionin a manner which will be described in detail hereinafter. Briefly,however, the present invention comprises operating a new automotiveengine or an engine which is substantially free of carbonaceous depositson a gasoline and a lubricant which will hereinafter be identified asnon contributing materials. The term non-contributing) as used herein isintended to designate those fuels and lubricants which formsubstantially no carbonaceous deposits when they are employed in anautomotive engine. Quantitatively speaking,'a non-contributing gasolineis considered to be a gasoline that possesses a resinification index ofless than 40 and preferably less than 20 mgs./200 g. A non-contributinglubricant is considered to be a lubricant that has a resinificationindex of less than 10 and preferably less than mgs./ 5 g. The exactdefinition of the term resinification index will be presented a littlelater in this description. The benefits of the present invention arebest realized when a new or clean engine is initially operated on acombination of a fuel that has a resinification index less than about 15mg./200 g. and a lubricant that has a resinification index of about 3mg./5 g. or less. It will be noted that conventional, commercialgradegasolines and lubricants have resinifieation indexes of about 40 to 100or more mg./200 g. and 25 to 60 or more mg./5 g. respectively. Fuels andlubricants in these latter ranges may be referred to as contributingfuels and lubricants, since they will contribute toward the octanerequirement increase of an engine in which they are employed.

The present invention further contemplates that the non-contributingfuel contain a hydrocarbon-soluble compounds of at least one of thefollowing metals: chromium, copper, manganese, zinc, nickel, cobalt,cadmium, molybdenum and iron. The metal compound, in addition to beinghydrocarbon-soluble, must be capable of forming an oxide of the metalunder the combustion conditions that exist within the combustionchambers of a conventional automotive engine.

In further accordance with the present invention, an automotive engineis operated on a metal-containing,

non-contributing fuel in combination with a non-contributing lubricant(of the types briefly defined above) for a period of time suflicient toprovide a layer of the oxide of the metal on the interior wall surfaceof each combustion chamber within the engine. The required length oftime will be brought out in detail later in this description. It iscritical, however, that this operating procedure be employed before theengine is operated on a fuel and/ or lubricant which would cause anybuildup. of carbonaceous deposits with the engine. In other words, it iscritical that any given automotive engine be operated in accordance withthe present invention before it is operated on a conventional fueland/or lubricant. As demonstrated later herein, the teachings of thepresent invention cannot be completely realized without adhering to thisoperating sequence.

As mentioned above, the present invention requires the use of gasolinesand lubricants that have resinification indexes of less than 40 mg./200g. and mg./5 g., respectively, preferably less than 20 mg./200 g. and 5mg./5 g., respectively, and especially less than mg./ 200 and 3 or lessmg./5 g., respectively. The term resinification index refers to therelative freedom of a fuel, lubricant or other material from a tendencyto form tenaciously adhering, resin-like, carbonaceous deposits when itis subjected to combustion in a container under a hot, smokeless flame,e.g., a hydrogen flame. In accordance with the Combustion Test forResinification Index (as described in detail in copending applicationSerial No. 352,373 filed in the name of Alexander H. Popkin on May 1,1953, now Patent No. 2,761,- 766) a known weight of a sample of materialto be tested such as a lubricating oil, a gasoline or other material isplaced in an open vessel having smooth nonabsorptive inner surfaces suchas a glass beaker, porcelain crucible, etc. A hot, smokeless, cleanflame and preferably a hydrogen flame (although other clean flames suchas methane, etc. may be used) is directed into the opening of thevessel. The burner tip, for introducing the gas and air or oxygen (ifneeded), is directed toward the interior of the vessel. The sample isburned until only a dry residue remains. The flame is discontinued andthe vessel is allowed to cool. The total weight of the resinous residueis then determined. When testing oils, the interior of the vessel iswiped carefully, before weighing, with a soft cloth or other softmaterial to remove carbonaceous deposits but to leave the tenaciouslyadhering resin-like deposits. The total deposits are weighed whenburning fuels. The weight of deposits in mgs. for a given weight orcharge in gms. gives the resinification index. Specific testingconditions used for oils, additive-containing oils, additives, and gasolines are shown below:

The combustion test described above has been found to accurately predictthe amount of combustion chamber deposits that a gasoline, lubricant orsimilar material will form within an automotive engine which is operatedunder actual road conditions. It has also been found to correlate withanother prediction test procedure which is carried out in a singlecylinder Lauson engine. The Lauson engine test in turn has been found tocorrelate with results obtained under actual driving conditions inconventional automobiles.

Single cylinder Lauson engines are well known in the art and are widelyused therein for various studies of petroleum lubricants, fuels and soforth. The particular Lauson engines employed in the tests that arereferred to in the present description had a 6.5/1 compression ratiohead and were operated with an induction motor at 1840 r.p.m. and 0.5BKW (brake-kilowatt) load.

Each test was usually run for a period of about 70-200 hours with theparticular lubricant or fuel being tested and with a spark advance of 12BTDC. The ratings were conducted with secondary reference fuels using anoscilloscope which gave visual ratings of knock intensity via asensitive pickup attached to one of the studs of the engine. Thisprocedure was found to be more accurate than the audio-type ratingsusually used in the Standard Uniontown procedure, because knocking inthe Lauson engine is difiicult to hear. Operations at the low powerlevel of 0.5 BKW have been established to provide good correlations withfull scale road tests. In other words, the Lauson engines experienceoctane requirement increases (O.R.I.) that are directly related (thoughnot necessarily equal) to the requirement increases that are experiencedby full scale automotive engines in actual road performance.

As described above, gasolines that are satisfactory for the purpose ofthe present invention include those gasolines which have aresinification index of less than 40 mg./20O g. Such gasolines may beproduced from fractions including isooctane; alkylate; virgin naphthasboiling below about 300 F. and preferably below 250 F.; high octanepolymers prepared by the catalytic polymerization of lower molecularweight olefins, hydroformates prepared by hydroforming naphthenic-typehydrocarbon distillates to form high octane aromatic components,reformed gasoline fractions prepared from straight run gasolines usingconventional platinum catalysts, metal oxide catalysts and the like;catalytic cracked naphthas prepared by cracking gas oils, residuals,etc., in the presence of metal oxide catalysts such as silica-alumina,silica magnesia, and the like; and various other types of comescapee'ponents that are conventionally employedin gasolines.

Such gasolines are usually formulated by mixing two or more of the abovegeneral types ofcomponents in order to form gasolines meeting octanerequirement, vapor pressure, stability, and other specifications.

It has generally been found of the various hydrocarbon 'cornpoundspresent in gasolines that parafiins, 'naphthenes and mono-olefins willnot contribute substantially to ORI. Aromatic components, particularlythose having a' boiling point higher than tolue'ne contributesubstantially to octane requirement increase. Those boiling above about300 F. are especially undesirable for this purpose. Therefore it ispreferred that the gasoline contain no more than 20% by weight ofaromatic hydrocarbons boiling above about 300 F., and more especiallyless than about 20% by weight of aromatics boiling above about 250 Leadtetraethyl is used in most commercial gasolines in concentrationsranging from about" 0.1 to 3.0 cc./ gallon Lead scavenging advantage indecreased ORI canbe achieved by lowering the sulfur content of gasolinecritically below the level at which the sulfur has any effect on theactual octane number of the gasoline containing tetraethyl lead. Forminimizing ORl'it is important to decrease the sulfur content of leadedgasoline below about 0.02% and pref erably below about 0.005% by weight.This may be achieved by treating the various components that go into thegasoline, in order to reduce the sulfur content to relativelynon-contributing amounts.

Treating procedures for sulfur reduction include prompt causticwashingofthe sulfur-containing material in the absence of oxygen soonafter a catalytic cracking operation; hydrofining of cracked naphthas inwhich the naphtha is treated with a catalyst in the presence ofhydrogen; treating naphtha with formaldehyde at elevated temperatureswith or without sulfuric acid; and treatment of sulfur-containingnaphthas with finely divided sodium in the presence of secondary orte'rtiary' alcohols, ethers or ketones. The'extent to which'any or allof'the components are treated 'will' of necessity 'depend' on the amountfuel is leaded with tetraethyl lead and non-contributing amountsofaromatics.

In order to minimize the contribution of a conventional leaded gasolinecontaining a normal complement of sulfur, say above 0.1% by weight, alead scavenging agent that is relatively high boiling may be added tothe fuel. Although it is conventional to use such materials as ethylene'dibromide and the like as scavenging agents, these materials are not soeffective for complete removal of lead as the higher boiling scavengingagents including halogenated aliphatic hydrocarbons such ashexacblorobutadiene; halogenated alkyl aromatics such as bromo xylenes,including mixed dibrornoxylenes, dibromo toluenes; 3,4dichlorocumene;l,2-'dibromobenzene; 1,2,4'trichlorobenzene; 2,4dichlorotoluene; theirmixtures and the like. Higher boiling means those agents having'substa'ntially the volatility characteristics of tetraethylleadipreferablythey 'have'vaporpressures at 120 F. of about 05m 5.0 mm.Hg. In' excess of about 0.5 and 'preferably above about1.0'stoichiometrical equivalents of these agents, based on the TEL, maybe added to the cate ""anddi-C 0x0 alcohol sebacate.

fuel. Such higher boiling scavenging agents are taught in such U .S.Patents as-2,496,983; 2,574,321 and 2,479,-

-The .gasoline fuel may also contain other addition agents such asantioxidants, guminhibitors, solvent oils, rust inhibitors, metaldea'ct'ivators, etc.

A gasoline fuel that is'particularly preferred for the purposes ofthe'pres'ent'invention is substantially pure iso-octane. Typical inspectionsfor such a fuel are presented in the following table.

'TABLE'I -Fuel' inspections Gravity, API 71.3 R.V.P.,p.s.i 1.8 Researchoctane'No 99.1 Motor octane No.- 98.8 Sulfur, weight percent 0.0008

Olefins, wt. percent 0 Aromatics, Wt. percent 0 Engler Distillation:

IBP 205 50% ofi, F. 210

FBP., F 264 1 Atmospheric pressure.

about 3 mgI/S g. Suitable lubricants have been presented,

described and claimed in Serial No. 375,158 filed in the nameorr'ednar'd E. Moody and Alexande'r'I-I. Popkin on August 19, I953.Suitable additive containing lubricants are described andclaimedinpatent application Serial'No. 375,138'filed in thena'me of LeonardE.Moody and Alex- "arider H. Popkin o'n August l9, 'l953, now abandoned.Thus, suitablelubricantsinclude distillate mineral lubricating oilfrac'tionsboilingbelowab'o'ut'S 75 F. at 10 Hg absolute) derived fromcrude oils which in turn are derived from an or Hie-conventional crudeoils. Those distillates derived from 'theMid-Continent fields, however,are preferred because of their excellent viscosity characteristics.

The preferred mineralbil'base stocks of the present tion at a pressureof 10 mm. Hg) have been removed. A suitable boiling ran'ge'is withinabout 275 to 575 F.,

"or'pr'efera'blywithin about 300 to575 F., at 10 mm. Hgpressure'absolute, with less than about 5 to 10% of 'co'mponentsboilingabove 550 F. and less than about 5 to 10% 'co'mponents boiling below 390F. The lower end of 'the'boiling range affectsto a large extent oilconsumption characteristics or the lubricant, and generallycomponentsboil'ingmuc'h below about 275F. to 325 F. at'10-'"mm.'Hgabsolute are too high in volatility for use in many high compressionratio internal combustion engines. The distillation testis lASTM MethodD 1160- 52 T.

Other suitable 'base' stock constituents and blending agents includelow' resinification index hydrogenated oils, synthetic oils resemblingpetroleum oils (polymerized ole- 'fins,'synthesis productsfromthe'reaction of oxides of carbon with'hydrogen or f'rom hydrogenatedcoals, shale oil derivative, etc.), formals, synthetic polyester andpolyether-type'lub'ricants and the like. Synthetic oils include estersmade from a monohydric alcohol and a monohydric organic acid or diestersmade from alcohols and dibasic acids. Specific examples includedi-2-ethylhexyl seba- Alcohols include the C C C C C and C alcohols madeby the 0x0 process'from' olefins. 'Suitable dibasic acids in- '7 cludeadipic, azaleic'and sebacic acid. Complex esters made from a monohydricalcohol, a dihydric alcohol (glycol) and a di'basic acid may also beused. Polyalkylene oxide-type synthetic oils, simple formals, complexfor- Gravity API 12.8 Viscosity SUS 100 F 178.0

210 F 48.6 Conradson carbon 0.098 Resinification index Pour pt. F -35'Ash 0.0057% (Wt).

The non-contributing fuels of the present invention must contain ahydrocarbon-soluble compound of at least one of the following metals:chromium, copper, manganese, zinc, nickel, cobalt, cadmium, molybdenumand iron. It is critically necessary that the hydrocarbon-solublecompound react under the conditions prevailing within the combustionchambers of a conventional automotive engine to form an oxide of themetal or metals selected.

Suitable compounds of the above metals include the gasoline-solublesalts or chelated compounds formed by their reaction with alcohols,phenols or organic acids. Preferred compounds are the metal derivativesof betadiketones; and particularly preferred compounds are thepentanediones of these metals.

An especially preferred fuel additive for the non-contributing fuels ofthe present invention is a mixture of about 80% by wt. of cobaltpentanedione and about by wt. of chromium pentanedione. The mixture ispreferably added to a fuel in the form of a concentrated solution in asolvent such as a non-contributing gasoline.

Other suitable additives include carbonyl compounds such as nickelcarbonyl, cobalt carbonyl, and iron carbonyl. Hvdrocarbonyls such asiron hydrocarbonyl and cobalt hydrocarbonyl may also be employed.

Summarizing momentarily, it is preferred that an automotive engine ofthe type described herein be operated on a lubricant consisting of anon-contributing motor oil of the polypyropylene oxide type and a fuelconsisting of isooctane containing a mixture of chromium and cobaltpentanediones. The automotive engine must be operated for a period oftime suflicient to provide a layer of metallic oxide on the surfaces ofeach combustion chamber that will be sufficient to prevent the formationof carbonaceous deposits thereon. This time period will vary dependingon the characteristics of the engine involved and the concentration ofthe additive in the break-in fuel. This time and additive concentrationshould be adjusted so that there will be consumed an amount of fuelequivalent to 0.01 to 1.0 grns. of the metallic element or elements persquare inch of clearance volume surface. An amount of fuel equivalent toabout 0.1 gms. of the metallic element or elements per square inch ofclearance volume surface is especially preferred.

The preferred concentration is such that the break-in procedure willrequire a maximum of ten and preferably less than five hours, althoughmany permutations may be used to suit the convenience of the operator.This is amplified further in the following examples.

The following examples are presented to more clearly illustrate thenature and advantages of the present invention. The examples wereobtained by using diiferent fuels and lubricants in variouscombinations. Each of the fuels and lubricants is described brieflybelow FUELS Fuel 1 consisted of substantially pure, syntheticallyprepared iso-octane.

Fuel 2 was a conventional commercial leaded gasoline consisting of ablend of iso-pentane, catalytically cracked naphthas, and virginnaphtha.

Fuel 3 Was another" conventional commercial motor gasoline comprising ablend essentially the same as Fuel 2.

LUBRICANTS Lubricant A was a synthetic lubricant of the polypropyleneoxide type.

Lubricant B was a commercial-grade motor oil which consisted of a blendof an extracted Mid-Continent distillate and a deasphalted, dewaxedresiduum.

Typical inspections of the fuels identified above are presented in thefollowing table:

TABLE II Fuel inspections Fuel 1 Fuel 2 Fuel 3 Gravity, API 71. 3 64. 059.0 R.V.P., psi l. 8 8. 5 8.5 Research Octane N0 99.1 94. 0 88.0 MotorOctane No. 98. 9 83.0 80.0 Sul ur, Wt. Percent 0. 0008 0. 07 0.08Olefins, Vol. Percent. 0 35. 40 30. 35 Aromatics, V01. Percent O 15. 20l0. l5 Resinification Index, Dig/200 g 13 Engler Distillation: IBP, F205 110 50% Off F 210 210 230 BR, F 264 380 410 l Atmospheric pressure.

Typical inspectionsof the lubricants described above are presented inthe following table.

TABLE III Lubricant inspections Example 1.A Lauson engine of the typedescribed earlier in this description was operated for a period of 73hours on Fuel 1 and Lubricant A. In this case, Fuel 1 contained 2.0 cc.per gallon of a solution comprising a mixture of chromium and cobaltpentanediones in a hydrocarbon solvent. This additive solution contained0.07 gram of the mixed pentanediones per cc. of solution distributed asfollows: 79.6 weight percent of the cobalt compound and 19.9% by weightof the chromium compound, and 0.5 weight percent unknown impurities.

At the start of the test the octane requirement of the clean engine wasdetermined by the use of secondary reference fuels in a conventionalmanner and was found to have an octane requirement of 47. After the73-hour operating period, the octane requirement of the engine was againdetermined and found to be still 47. These results clearly establish thefact that the lubricant and the fuel were both non-contributors and thatthe addit-ive employed had no adverse effect on the octane requirementof the engine.

Example 2.The engine employed in Example 1 was again operated on Fuel 1and Lubricant A but in this this instance the fuel contained 100 cc. pergallon of the additive described in Example 1. In this instance, theengine was operated for a period of 2.5 hours for the IExdmple-?3.Afterthesteps'de'scribed in Examples 1 r"- and 2 were completed, the Lausonengine described in those examples was then operated for a period ofabout 80 hours on Fuel 1 containing no additive and Lubricant B.Following the 80-hour period of operation, the octane requirement of theengine was determined and found to have remained at a value of 47. Thus,the preformation within the combustion chamber of the layer of cobaltand chromium oxides operated successfully to completely eliminate anyincrease in the octane requirement of the engine when it was switched toa lubricant which had been found to be a definite offender in thisregard. The extent to which this conventional lubricant is an offenderis brought out more clearly in Example 6 which is presented laterherein.

Example 4.A Lauszon engine with an initial octane requirement of 54 wasoperated for a period of 182 hours on a combination of Fuel 2 andLubricant A. The fuel in this instance contained 4 cc. of a gallon ofthe additive described in Examples 1 and 2. Unlike the results obtainedin those examples, however, the engine in the present exampleexperienced an increase in its octane requirement about octane numbersafter 44 hours of operation, and 14 octane numbers after 182 hours ofoperation. It is apparent from. these results that the use of the fueladditives that are specifically advocated in the present description isnot effective in preventing an increase in the octane requirement of anengine unless the additives are introduced within the engine before theengine is operated on fuel and/or lubricant compositions that are knownto be offenders in this respect. In this instance the lubricant was anon-contributor but the fuel was a definite contributor.

Example 5 .A Lauson engine having an initial octane requirement of 56was operated for a period of 190 hours on Fuel 1 and Lubricant B. After70 hours. of operation, the octane requirement of the engine increasedto a value of 64. After 190 hours, the octane requirement of the engineincreased to: a value of 73. It is clear from the data obtained in thisexample and in example 3, above, that the fuel additives of the presentinvention are extremely effective in reducing the octane requirement ofan engine when the procedure for introducing the additives within theengine which is spelled out in the present description is adhered to.Thus, it will be observed that the engine of Example 3, which wasoperated on the same fuel and lubricant composition as the engine in thepresent example, experienced no increase in its octane numberrequirement. The engine in the present example, on the other hand,experienced an octane requirement increase of about 8 units after beingoperated for substantially the same period of time as the engine inExample 3.

The present example also clearly demonstrates that the octanerequirement of an engine will increase very substantially if the engineis operated on a lubricant that has a high resinification index. Thisresult will occur even though the fuel in the engine is of thenon-contributing type.

Example i6.-In this example a conventional Plymouth engine was operatedon Fuel 3 and Lubricant B for 3500 miles. The octane number requirementincrease experienced by the engine in this instance was 8.4 octanenumbers.

The engine was then overhauled, and the deposits existing in thecombustion chambers of the engine were completely removed. The enginewas then operated for another 3500 miles on Fuel 3 and Lubricant B, butin this instance the fuel contained 4 cc. per gallon of the additive 10described inExam'ple 1 above. D'firing'this'test the octane requirementof the engine increased 9.5 octane numbers, thereby again demonstratingthat it is a critical feature of thepresent invention to (1) operatethe'engine initially on non-contributing fuels and lubricants in' combi-natio'n and (2)'to incorporate within the non-contribuh ing fuel thepresently defined additives.

It will be particularly noted that the data obtained in the presentexample agree very well with the data obtained in Example 4 in that bothexamples show that it is substantially useless to employ the fueladditives of the present invention without also employingnon-contributing fuels or lubricants during the initial operation of theengine.

What is claimed is:

l. A method of operating an internal combustion engine having acompression ratio of at least about 7/1, which comprises initiallyoperating the engine on a noncontributing lubricant having aresinification index less than 10 ing/5 g. and a non-contributinggasoline having a resinification index less than 40 mg./200 g.; saidnoncontributing gasoline containing a gasoline-soluble metal compoundselected from the class consisting of the gasoline-soluble compounds ofchromium, copper, manganese, Zinc, nickel, cobalt, cadmium, molybdenumand iron; said compound being of a character to provide an oxide of themetal under the conditions within the combustion chambers of the engine;and thereafter operating the engine on a gasoline and lubricantcombination ordinarily forming excessive deposits within the combustionchambers of the engine.

2. A method as defined in claim 1 in which the engine is operated on thenon-contributing gasoline and lubricant for a period of time adapted toconsume from 0.01 to 1.0 gms. of the metal in the metal compound persquare inch of clearance volume surface in the engine.

3. A method as defined in claim 2 in which the gasoline is iso-octaneand the non-contributing lubricant is a synthetic oil of thepolypropylene oxide type.

4. A method of operating an internal combustion engine that has acompression ratio greater than 7/1 which comprises initially operatingthe engine on a non-contributing gasoline having a resinification indexless than 40 mg./20O g. in combination with a non-contributinglubricating oil having a resinification index less than 10 mg./5 g.;said gasoline containing a gasoline-soluble metal compound selected fromthe class consisting of the gasoline-soluble compounds of chromium,copper, manganese, zinc, nickel, cobalt, cadmium, molybdenum and iron;said metal compound being adapted to form an oxide of the metal underthe conditions that prevail within the combustion chambers of theengine; consuming an amount of said gasoline equivalent to from about0.01 to 1.0 gms. of the metal per square inch of clearance volumesurface in the engine; and thereafter operating the engine on aconventional gasoline having a resinification index greater than 40mg./200 g. and a conventional lubricant having a resinification indexgreater than 10 mg./5 g.

5. A method as defined in claim 4 in which the noncontributing gasolinehas a resinification index less than 20 mg./200 g. and thenon-contributing lubricant has a resinification index less than 5 mg./5g.

6. A method as defined in claim 5 in which the noncontributing gasolinehas a resinification index less than 15 mg./ 200 g. and thenon-contributing lubricant has a resinification index of about 3.

7. A method as defined in claim 6 in which the gasoline-soluble compoundis a pentanedione.

8. A method as defined in claim 7 in which the compound is a mixture ofcobalt pentanedione and chromium pentanedione.

(References on following page) References Citedin the file bf thispatent 7 UNITED STATES, PATENTS Barnard Dec. 15, 1942 12 Malott Dec. 12,1944 Taylor July 26, 1949 Bartleson July 17, 1951 Hays Nov. 9, 1954Trimble et a1. Sept. 4, 1956

1. A METHOD OF OPERATING AN INTERNAL COMBUSTION ENGINE HAVING ACOMPRESSION RATIO OF AT LEAST ABOUT 7/1, WHICH COMPRISES INITIALLYOPERATING THE ENGINE ON A NONCONTRIBUTING LUBRICANT HAVING ARESINIFICATION INDEX LESS THAN 10 MG./5 G. AND A NON-CONTRIBUTINGGASOLINE HAVING A RESINIFICASTION INDEX LESS THAN 40 MG./200 G., SAIDNONCONTRIBUTING GASOLINE CONTAINING A GASOLINE-SOLUBLE METAL COMPOUNDSELECTED FROM THE CLASS CONSISTING OF THE GASOLINE-SOLUBLE COMPOUNDS OFCHROMIUM, COPPER, MANGANESE, ZINC, NICKEL, COBALT, CADMIUM, MOLYBDENUMAND IRON; SAID COMPOUND BEING OF A CHARACTER TO PROVIDE AN OXIDE OF THEMETAL UNDER THE CONDITIONS WITHIN THE COMBUSTION CHAMBERS OF THE ENGINE;AND THEREAFTER OPERATING THE ENGINE ON A GASOLINE AND LUBRICANTCOMBINATION ORDINARILY FORMING EXCESSIVE DEPOSITS WITHIN THE COMBUSTIONCHAMBERS OF THE ENGINE.